VSS Connectivity with another VSS

[jahanzaib amin]

Dears,

I would like to confirm about the VSS structured design. Can we connect 2 VSS back to back as Core and Distribution? I review 1 Cisco document which  give me only limited information with only that the Domain IDs will be different on both back to back VSS connected Pair. 

I want to confirm that what is the connection between the 6500 (VSS) and 4500-x (VSS). Can we connect as Layer-2 Port Channel between Catalyst 6500 and Catalyst 4500-X? Access layer work as layer-2 and connect with 4500-X as well. So the SVIs stay on Core (6500)?

Or We can connect both VSS Pair as Layer-3? If yes then SVIs stay on 4500-X?

Thanks,

[ahmedshoaib · Accepted solution]

Hi;

For back to back VSS you just need to care about VSS domain id, it should be different.

with reference to connectivity b/w 2 VSS it can be either L2 port-channel L2 or L3 it's depend on your requirement.

Thanks & Best regards; 

[devils_advocate · Accepted solution]

Yes, you can use a VSS pair at the Core layer and another VSS pair at the Distribution Layer.

They can be Layer 2 or Layer 3, if you are following 'best practice' then it would be best to go Layer 3. Realistically you shouldn't be spanning Access Vlans up to the Core but it depends on your requirements. 

The purpose of the Core layer is high speed forwarding, you want your SVI interfaces for your VLAN's to terminate on the Dist switches and ideally have Layer 3 routing between this and the Core Layer.

Presumably you have other 'Networks' connecting into the core like the Data Centre network and/or the Internet edge etc?

If you literally have all your Vlans (Users, Servers, Internet etc) on your Access switches which are piped into the Dist layer then do you even need separate Core switches? Perhaps a collapsed core might be the way forward. 

[jahanzaib amin]

Hi,

There are 20 Access Switches for Users, so if keep their all SVIs on distribution (4500-x) and connectivity as L2 in between Distribution and Core. Further put the static route on Core and distribution with 1 Vlan which will do the routing in between Distribution and Core?